As a conventional rotatable connector using flat cables as mentioned above, an already proposed rotatable connector (see Patent Document 1), for example, has a structure in which a reversed part of flat cables accommodated in a ring-shaped space is guided by a rotatable roller axially supported by a holder (retainer) and a guide wall projecting in the vicinity of the rotatable roller.
In more detail, as shown in FIG. 8, an outside wound part Co of the above-mentioned flat cables C is accommodated in the ring-shaped space in the state of being wound along an inner circumferential surface of an outer cylindrical body 61 of a stator member. An inside wound part Ci of the flat cables C is accommodated in the ring-shaped space in the state of being wound along an outer circumferential surface of an inner cylindrical body 62 of a rotor member. A reversed part Cr of the flat cables C is wound along one rotatable roller 63 axially supported by a holder. The rotatable holder 63 along which the reversed part Cr is wound is located on a reference line D passing axial centers P of a plurality of other rotatable rollers 63 located concentrically with the holder in a circumferential direction of the holder.
When the rotor member of the rotatable connector having the above-described structure is rotated in a clockwise direction, the reversed part Cr of the flat cables C is pressed on a guide wall 64, and the pressing force causes the holder to rotate in the clockwise direction. When the rotor member is rotated in a counterclockwise direction, the reversed part Cr of the flat cables C pulls the rotatable roller 63, along which the reversed part Cr is wound, in the counterclockwise direction, and the holder is rotated in the counterclockwise direction.
With the above-described structure, the outside wound part Co of the flat cables C wound along the inner circumferential surface of the outer cylindrical body 61 does not have any inflection point, but the inside wound part Ci of the flat cables C wound along the outer circumferential surface of the inner cylindrical body 62 has an inflection point. Therefore, the curvature deformation ratio across the inflection point of the inside wound part Ci is gradually increased in a downstream direction and an upstream direction with respect to the inflection point.
Accordingly, when the rotor member is rotated in the clockwise direction, the reversed part Cr, having a large curvature deformation ratio, of the flat cables C is regulated in the state of being pressed to an outer corner of the guide wall 64 or the vicinity thereof, and the flat cables C is fed while the reversed part Cr thereof is slid on the outer corner of the guide wall 64 or the vicinity thereof.
Namely, the reversed part Cr of the flat cables C and the guide wall 64 are in point contact or in line contact with each other. Therefore, the contact area between the reversed part Cr and the guide wall 64 is small, and thus the reversed part Cr of the flat cables C is slid in the state where a part of the reversed part Cr receives a load (reaction force) from the retainer in a concentrated manner. For this reason, when the connector is operated to rotate repeatedly, lamination covers of the flat cables C are likely to be worn. Thus, there are problems that, for example, conductors exposed by the wearing may be shortcircuited or broken.